Invitation to CodeChef Starters 114 (Rated till 6-stars)

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Invitation to CodeChef Starters 114 (Rated till 6-stars) — 27th December

Автор JaySharma1048576, 5 месяцев назад, По-английски

We invite you to participate in CodeChef’s Starters 114, this Wednesday, 27th December, rated till 6-stars (i.e. for users with rating < 2500).

Time: 8:00 PM — 10:00 PM IST

Joining us on the problem setting panel are:

Setters: Kanhaiya notsoloud1 Mohan, Arnob Arnob Sarker, Aryan Dutt, Aniruddh Chimpanzee, Rudro Rudro25 Debnath, Shivam Goyal, Takuki tabr Kurokawa.
Tester: Yash yash_daga Daga
Statement Verifier: Kanhaiya notsoloud1 Mohan
Text Editorialists: Nishank IceKnight1093 Suresh.
Contest Admin : Jay JaySharma1048576 Sharma.

Written editorials will be available for all on discuss.codechef.com. Pro users can find the editorials directly on the problem pages after the contest. The video editorials of the problems will be available only to Pro users.

Also, if you have some original and engaging problem ideas, and you’re interested in them being used in CodeChef's contests, you can share them here.

Hope to see you participating.

Good Luck!

JaySharma1048576
5 месяцев назад
27

Комментарии (27)

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mohamedeltair

5 месяцев назад, # |

← Rev. 3 →

+14

Was this announcement invalid or was the contest originally 1 hour and 45 minutes :D

"The contest is extended by 15 minutes due to this issue."

Update: Looks like the contest ended and then resumed again for the remaining 15 minutes ...

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_Gawd_

5 месяцев назад, # |

which case I'm missing for problem game on array.

code

void solve(){
    int n;
    cin>>n;
    int arr[n];
    long long od_sum=0,ev_sum=0;
    for(int i=0;i<n;i++){
        cin>>arr[i];
        if(i&1)ev_sum+=arr[i];
        else od_sum+=arr[i];
    }
    if((od_sum+ev_sum)%2==1)cout<<"Bob\n";
    else  {
        long long bmove=(od_sum+ev_sum-2)/2;
        if((bmove%2)==0){
            if((od_sum%2)==0)cout<<"Bob\n";
            else cout<<"Alice\n";
        }
        else{
            if((od_sum%2)==1)cout<<"Bob\n";
            else cout<<"Alice\n";
        }
    }
}

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chiki_2d

5 месяцев назад, # ^ |

You have to handle n==1 seperately lmao

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isnotavail

5 месяцев назад, # ^ |

← Rev. 2 →

it's probably n = 1

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Barbareek_3

5 месяцев назад, # ^ |

Hey Can you Explain your approach.

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BF_OF_Priety

5 месяцев назад, # ^ |

to find that observation do dp on smaller constraints

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idkwhatonearth

5 месяцев назад, # |

+34

Thank you for creating yet another "OBSERVE THE PATTERN with weird edge cases" round :).

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frissky9

5 месяцев назад, # |

+50

The "YET ANOTHER MATRIX PROBLEM" was too stupid. Idk i have no words but it was an awful problem.

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handleisinuse

5 месяцев назад, # ^ |

It ruined my mood ngl

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aryan12

5 месяцев назад, # |

So much mindless implementation with figure out what are the edge cases.

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Pirate_King

5 месяцев назад, # |

-10

i HATE constructive problems

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hackerbhaiya

5 месяцев назад, # |

+21

I submitted the correct partial solution at the start (25 minutes from the start of the contest): https://www.codechef.com/viewsolution/1037176417

I was getting the wrong answer for almost an hour. Extension by 15 minutes which also didn't happen at least till 1-2 minutes after 10 p.m. and also these 15 minutes can't compensate for the loss of 1 hour in which I was completely exhausted and lost the tempo, where I was trying to find the bug and consistently submitting the code for another one hour which was actually correct for subtask 1.

I don't see any reason to make the contest rated for the participants who were affected by this mistake.

CodeChef_admin can you please give a logical explanation behind all these? Don't you think it was too early to announce (21:40, i.e., 20 mins before the end of the contest) that solutions are rejudged?

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CodeChef_admin

5 месяцев назад, # ^ |

+14

Figuring out who were affected is a non-trivial process and takes time. It should be done by tonight.

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CodeChef_admin

5 месяцев назад, # ^ |

An email was sent to the 21 adversely affected participants, and the contest has been made unrated for them.

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piyush_pransukhka

5 месяцев назад, # ^ |

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AGRU

5 месяцев назад, # |

For the problem YET ANOTHER MATRIX PROBLEM, can anyone explain their solution and more importantly how they came to it?

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granadierfc

5 месяцев назад, # ^ |

I think to come for such solutions is to do smaller cases , like n = 3 , 4 , 5 , etc.When building the matrix , we can place 1(for odd) or 0(for even) in the cells. The approach is to keep few 1s in matrix which satisfies conditions and then add more 1s preserving the conditions. Now I observed that for odd n , we can place all the 1s on the 1st row and 1st column i.e. first place a[1][i] = 1 and a[i][1]=1 , let others remain 0 for time being. You can see this satisifes for odd n. Now we can place 1s in pair so that a particular submatrix border cells increases by 2 until the number of 1s become (n^2 + 1)/2. in even case there will be a problem with this construction as initially number of 1s = 2n — 1 , but when we add 1s in pair the number of 1s will finally be odd , which will be a problem in even case. Hence we can put a[1][n-1]=0 and put a[n-1][n-1]=1 and a[n][n]=1. Now for even this satisfies the required conditions all we need to do is to keep adding 1s in pairs.

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AGRU

5 месяцев назад, # ^ |

Thanks for the detailed explanation, pretty good approach of taking minimum numbers of 1 first then adding more according to the need.

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granadierfc

5 месяцев назад, # |

In the problem Make Same , what does proper substring mean? Can a string be called as one of the proper substrings of itself?

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JaySharma1048576

5 месяцев назад, # ^ |

It is given clearly in the statement — "Note that a substring $$$u$$$ is said to be a proper substring of string $$$v$$$ if $$$u\neq v$$$."

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granadierfc

5 месяцев назад, # ^ |

sorry , didn't see that

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tautology

5 месяцев назад, # |

Can someone from Codechef explain the penalty in starters? I don't see it on the contest page.

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CodeChef_admin

5 месяцев назад, # ^ |

Not sure where you are looking. There's a "Rules and Regulations" section in the contest page which explains this in these two points:

You can submit solutions as many times as you'd like, there are no penalties for incorrect submissions. Only your best correct submission will be considered.
Those who achieve the score first will be placed higher in the ranklist in case of a tie.

So that basically means that the tie-breaker is just the time when you achieved your final score. And that's displayed in the ranklist as the column "Last AC".

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tautology

5 месяцев назад, # ^ |

Oops, my bad. Thanks for pointing it out.

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handleisinuse

5 месяцев назад, # |

-6

The idea of hiding editorials behind paywall is disheartening to see, it hinders a fostering collaborative learning environment. I would humbly request anyone skill-full to write an editorial for us, all i can offer is love and blessings.

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